Ice removing apparatus for airfoils



April 27, 1948.

J. O. ANTONSON ICE REMOVING APPARATUS FOR AIRFOILS Filed March' 21. 1944 Patented Apr. 27, 1948 ilonznEMovNiG' formamos ron Marions Jolni0. Antonson, Akron, l(ll'iio, assignor to. The B. F. Goodrich'Company, New York, N. Y., a

corporation o'f New York Y Applcation Marc'shfl, 1944, `SeriaillNo. 527,38'8

` (llaims. (01..-244-134) This invention relates topzprotective 'apparatus forairfoilsrfand especially lto'rir-iiiatable apparatus for preventing the #accumulation olf. ice thereon.

While prior constructionsofintlatable tapparatus mounted at the `learlingfedges of wings fand other airfoilshavebeen utilized advantageously in ice prevention under most conditions, the action of such fapp'aratusunderwsome icingcon'di- 'tions "of particular severity ll-asnot been 'effective to `"obtain 'the desired' *Eull'cleanlinesso'f ice removal and 'ice :caps havefat 'times not been broken andremoved with the tullipromptness andtho'roughne'ss desired.

Y"Cflxlects 'of 'this invention are `to provide improved apparatus iter-preventing with :increased effectiveness the accumulation of ice 'onthele'ad- `ing fedge of an airf'oil'.; to provide -for promptly breaking and `loosening ice caps on the leading,r

edgelfor theirremovali-by .'tli'elambi'ent airstream.; 4

to provide for imparting :substantial stretching force to a' stretchable lportion rearward of. an Yei;- pa'nsiblezone `during "a "phaseof the expansion of such zone and for exerting little-or 'no stretching force on 'the 'stretchabl'e portion-during -a subsequent phase of such expansion; to provide for expanding locally a aportion of the expansi'ble zone 'to arelatively high degree'of curvatureas compared to the curvatureof `adjacent*expansibie portions upon expansion 'fof' the latter; to provide for maintaining the Adesired aerodynamic characteristics ofthe 'airfoifh 'andtoprovide thin,- ness and simplicity `of construction, convenience of manufacture and'feife'ctiveness of operation.

These `and other objects and advantages 1of the .invention will be Vapparent from the following description.

lIn kthe acoomparrying'drawing's which form a part of this specification and in which like numerals are employed to designate like parts throughout'the same, f Y

fFig. "1 is a `perspective view of `protective apparatus mounted onthe' leadingedge of vvan airplane wing, and constructed .in accordance with and vembodying vthe invention, :parts being broken away and in section,

Fig. 2 vis a plan viewrfrom above of the apparatus or covering before beingV installed on the wing, parts being broken away,

Fig.. 3 is. a cross-sectional view-of the covering installed on 'the wing showing a cap-breaking tube `in the linflated condition with little or no stretching-of the stretchable portions rearwardly of such tube, and A Fig. 4 is a view like Fig. 3 but showing a pair of associatedv stretching tubes inthe inflated conv lof elastic construction including resilient rubber .I2 or other rubber-like-material is mounted on vthe leading Vedge -of Va wing l l Jof an airplane, ffor example, 4the winghaving a nacelle lf2 housing a motor for ldriving a .propeller t3.

The covering ll Ulis mounted in na stretched condiii'on 'inthe chordwis'e direction-ofthe wing Il and 'secured --to the wing skinfalong upper and lower attaohingimargins I4 and H'rof `thecoveringextending sp'anwise of the wlng'as-by attaching screws 16 vextend-ingthrough upper and lower marginal fair-ing strips l1, t1 and through the coveri-ngsl and Ii-rito thewlng skin. The attaching margins |'4,' I5may have reinforcing strlpsfor b'eadvelements 18, I8-of stiff material such, for example, as fla-t'metal Awirei-ncluded therein.

The covering which .has a relatively smootnextenor-surface forpromotingsmooth ilow of the ambient air, includes an expansible or central tubel'zon-e `I9 intermediate the attaching margins and stretchab-le lportions 2l), 2-l extending-rear- Wai-idly -froinsuchzone. The `covering also includes-'a'pluralityof inflatable tubesf-2-2,-23,'2# disposed in the-tube zone`l9 in series in the chord'- wise f'dire'c'tion forlocal'e'iqaandirrg` of` the -zone I9 andY for `stretchingthe--stretcliableportions 20, -2 I uponinflationof the respective tubes in a cyclic manner "described hereinafter. For inflating `tlie tubes, 'connector means 25 in communication with such tubes atone end-of thelatter maybe provided. Fluid `conduits -2'5 and 21 are connected to the 'connector means 25 and tol suitable` control equipment `(not shown) and to a source of air under pressurewhich equipment and source o'f 'air'm'ay be disposed, for example, withinv the fuselage fof the airplane. The innersurfacevof the body of the covering lil fm'ay be :provided vwithventing `channels 28 extending inthe spanwis'e Vvdirection 'and `spacedap'art ven-tingrgroovesl 29 extending` in the chord- -Wis'e 'direction, venting 'aiiertures 3l) being in communication with the outer air at spaced- `apart positions Aclrordwise along, such venting grooves. This subject matter-of `the channels and the 'grooves for venting action i-s set forth Vmore fully the 'copendin-g Yapplication of WillsonvH. Hunter. and: William C. Green, Serial No. 482,536, "filed vApril 1'0,.1943,'now matured intoPatent-No. 2,421,621', `issuedJ1-mei?, 1947-. Y

The *cap-breaking. tube `t3 may be relatively smallin Across-sec-tion. as compared to the spaced- 'apart stretching tubes I217,211 which'may `bci-larger in 'cross-section. They cap-breaking tube 23 is 'positioned between the stretching tubes 22, 2l-in series chordw'i-se therewith I for'local stretching of Vthe `covering- ,r at the tube zone with little or Yno stretching of the stretchable portions 20., 2l. These tubes `.22, 213, Zllmay -be tapered spanwise in. conformance with the tapered-arrangement of the covering I9 as shown especially vlig. The cap-breaking tube `2:. is disposed preferably immediately at the leading edge and has a wall of relatively great stretchability as compared to the associated stretching tubes 22, 24. Such wall includes in therubber thereof reinforcing material such as stockinette or other knitted or otherwise stretchable fabric, preferably of nylon or rayon, although cotton or other suitable material may be used. The stockinette fabric is stretchable both circumferentially and longitudinally of the tube, which permits extensivev stretching of the tube wall for expanding the covering locally at the tube zone to break and loosen the ice cap thereon.

For facilitating such local expanding action, it is desirable that the cap-breaking tube 23 be disposed within the covering immediately beneath the outer surface of the latter in the tube zone whereby a relatively thick body of rubber material is under such tube 23 as compared to the adjacent tubes 22, 24; whereas the latter tubes 22,24 are disposed desirably immediately adjacent the inner surface of the covering whereby a relatively thick body of rubber material is over these tubes, 22, 24 as compared to the tube 23.

This construction is advantageous in that the tube 23 upon inflation first in the cycle tends to expand and stretch outwardly and to assume the relatively high degree of curvature afforded by a semi-circular shape in section as shown in Fig. 3, by virtue of the uniform and high stretchability of the wall thereof and also by virtue of the little or no restraint against local stretching offered bythe thin resilient rubber of the covering over suchtube 23. A further advantage of the construction described hereinabove is that the inner part of the covering at the tube zone I9 and the stretchable portions 20, 2| remain against the wing with negligible lifting therefrom during the inflation of the cap-breaking tube 23 thereby7 avoiding objectionable entrapment of air, especially at the tube zone, and subsequent objectionable ballooning of the covering. Also the stretching of the tube 23 is effective at the immediate leading edge region in cracking and loosening the ice cap even though the ice cap be heavy, but in this rst part of the cycle need have little or no effect on rearward ice formations on the'stretchable portions 20, 2|.

The spaced-apart stretching tubes 22, 24 adjacent the opposite margins of the tube 23 have rubber walls including stretch-resisting textile fabric material, preferably square-woven fabric, straight-laid, for limiting the expansion of the tubes 22, 24, such fabric being relatively inextensible as compared to the fabric included in the tube 23. Such expansion-limiting or stretchresisting fabric reinforcement resistsV effectively the local stretching of the rubber walls, and the tubes 22, 24 upon inflation assume an outwardly curved shape of lesser sharpness of curvature than that of the tube 23 as shown in Fig. 4, and

` move laterally relative to the leading edge by virtue of their spaced-apart positioning at such leading edge. This action further assists removal of any remaining broken pieces of the ice cap by moving such pieces laterally into the airstream; and'this action also effectively imparts a relatively great stretching force to and uniformly throughout the extent of the stretchable portions 20, 2| and moves the latter portions outwardly from the wing I I whereby the sheet-like ice forfmations on the stretchable portions are broken and loosened for prompt and thorough removal by the ambient airflow. The stretchable portions 20, 2| comprising 4 suitable rubber-like material extend rearwardly from the tube zone I9 to the attaching margins I4, I5 and include desirably'spaced-apart tearresisting strips 3|, 3| of chordwise stretchable fabric material such, for example, as Trico fabric embedded therein. The strips 3| may be located at the venting grooves 29 and extend chord- Wise between the margins of the stretching tubes 22, 24 and bead holding elements 32, 32 of chordwise stretchable fabric material at the attaching margins I4, l5. The stretchable fabric of the bead holding elements 32, 32 is folded around the wires I8, I8 and permits stretching of the stretchable portions 20, 2| directly to and along the bead wires I8, I8 for promoting uniformity of stretch of such portions and for uniformly stressing such wires. 'An offset in the covering may be provided for a` flush mounting of the fairing strips Il, Il.

' The fabric andrubber parts of theV covering are united by vulcanization and heat under pressure.

In the operation of the apparatus Ill, it is desirable that the cap-'breaking tube 23-be inflated rst in the cycle by admitting air under pressure through the conduit 21 and connector means-V25. The tube 23 then distends outwardly to a substantially semi-circular shape in cross-section in the manner shown in Fig. 3, the wall of the tube stretching locally`to a. relatively great extent Within itself by virtue of the stretchable action of the nylon fabric. Such distending and stretching action of the tube .23 Yexerts little or no stretching force upon the stretchable portions 20, 2| but cracks and loosens effectively the ice cap although the inflation of the tube 23 need have little or no eifect on rearward ice formations on such portions 20, 2|.

After deflation of the tube 23, the next phase in the operation of the apparatus is the inflation of the stretching tubes 22, 24, preferably simultaneously, by the air under pressure flowing through the conduit 26 and the connectors 25. These stretching tubes 22', 24 distend outwardly and move laterally relative to the leading edge because .of their spaced-apart positioning thereon, and assume an expanded condition substantially as shown in Fig. 4, since the walls of the tubes include expansion-limiting fabric `reinforcement which is relatively inextensible. Such action facilitates removal of any vremaining broken pieces of the ice cap by moving such pieces laterally into the airstream and imparts relatively great stretching force to the stretchable portions 20, 2| while movingY such portions outwardly relative to the wing, whereby the stretchable portions are stretched effectively throughout their extent thus breaking and loosening the ice formations thereon into pieces for removal by the ambient airflow over these portions of the covering. 'The construction and arrangement'of the apparatus hereinabove described prevents effectively the accumulation of ice on the leading edge of the wing while maintaining the desired aerodynamic characteristics of such wing."

Variations may be made without departing from the scope of the inventionV as it is defined in the following claims:

Ilclaim:

l. Apparatus for preventing the accumulation of ice on the leading edge of an airfoil,A said apparatus comprising a covering of resilient '-r'ubber-like material for said leading edge having 'an expansible zone and a stretchable portionlie'- tween said zone and a margin of thecc'nve'ring,

and means for attaching said covering at said margin, the covering in said expansible zone including a plurality of adjacent inflatable portions extending spanwise in side-by-side relation along the covering and serially arranged in the chord wise direction, at least one of said inflatable portions including stretch-resisting material and being constructed and arranged for imparting upon inflation a stretching force to said stretchable portion, and another of said inflatable portions to one side of the first inflatable portion having a margin thereof extending along in close proximity to an adjacent margin of the rst said inilatable portion and including material of relatively high stretchability as compared to said stretch-resisting material of the first said inflatable portion and being constructed and arranged for local inflation by virtue of its high stretchability without exerting substantial stretching force on said stretchable portion.

2. Apparatus for preventing the accumulation of ice on the leading edge of an airfoil, said apparatus comprising a covering of resilient rubber-like material for said leading edge having a spanwise-extending tube zone and a spanwiseextending stretchable portion between said zone and a spanwise-extending margin of the covering, means for attaching said covering at said margin, a pair of inflatable tubes spaced-apart chordwise and extending spanwise along the covering in said zone, said tubes comprising stretchresisting fabric material and being constructed and arranged for imparting upon ination a stretching force to said stretchable portion, and an inflatable tube extending spanwise along the covering in the space between and in side-by-side relation with the pair of inflatable tubes in said zone and comprising fabric material of relatively high stretchability as compared to that of said stretch-resisting fabric material of the pair of inflatable tubes and being constructed and arranged for local inflation by virtue of its high stretchability without exerting substantial stretching force on said stretchable portion.

3. Apparatus for preventing the accumulation of ice on the leading edge of an airfoil, said apparatus comprising a covering ,of resilient rubber-like material for said leading edge, said covering comprising a tube zone intermediate the margins of the covering and stretchable portions extending rearwardly from said zone toward said margins at opposite sides of said tube zone, means for attaching said covering at said margins, a pair of spaced-apart inflatable 4tubes extending along the covering in said zone, the pair of inflatable tubes including stretch-resisting fabric material in the walls thereof and being constructed and arranged for imparting upon inilation a stretching force to said stretchable portions, and an inflatable tube extending along the covering in the space between said pair of inilatable tubes in side-by-side relation therewith in said zone and including fabric material in the wall thereof `of relatively high stretchability as compared to that of said stretch-resisting fabric material of the pair of inflatable tubes and being constructed and arranged for local inflation by virtue of its high stretchability without exerting substantial stretching force on said stretchable portions.

4. Apparatus for preventing the accumulation of ice .on the leading edge of an airfoil, said apparatus comprising an elastic covering including resilient rubber-like material for said leading edge having an expansible zone extending along the covering and a' stretchable portion between said zone and a margin of the covering, and means for attaching said -covering at said margin, the covering in said expansible zone comprising a pair of spaced-apart inflatable portions extending along the covering in said zone each including a, stretch-resisting material therein and being constructed and arranged for imparting upon inflation a stretching force to said stretchable portion, and the covering in said zone comprising an inflatable portion extending along the covering in the space between the spaced-apart inilatable portions in said zone and having the `margins of said inflatable portion in close proximity to adjacent margins of said spaced-apart inflatable portions, said inflatable portion being of lesser width than that of each of said spacedapart inflatable portions and including fabric material of relatively high stretchability as compared to that of said stretch-resisting fabric material and being constructed and arranged for local inflation by virtue of its high stretchability without exerting substantial stretching force on said stretchable portion.

5. Apparatus for preventing the accumulation of ice on the leading edge of an airfoil, said apparatus comprising a covering cf resilient rubber-like material for said leading edge having a tube Zone extending along the covering and a stretchableportion between said zone and the margin of the covering, means for attaching said covering at said margin, a pair of inflatable tubes spaced-apart chordwise and extending spanwise along the covering in said zone, said tubes including stretch-resisting fabric material in the walls thereof and being constructed and arranged for imparting upon inflation a stretching force to said stretchable portion, and an inflatable tube extending spanwise along the covering in the space between the pair of inflatable tubes in said zone and being the sole inflatable means in said zone between said pair of inilatable tubes, said inflatable tube being of lesser width than that of each of said pair of inflatable tubes and including fabric material in the wall thereof of relatively high stretchability as compared to that of said stretch-resisting fabric material and being constructed and arranged for local inllation by virture of its high stretchability without exerting substantial stretching force on said stretchable portion.

JOI-IN O. ANTONSON.

REFERENCES CITED The following references are of record in the le of this patent:

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